32,767 is the limit of a short, not of an int. The limit of the latter is 2,147,483,647 and it is probably the limit of an array as well, as long as the memory is big enough.

Okay, I thought ints were 16 bit. Thanks a lot for your patience, PhiLho, vous êtes genoux de l'abeille.

Mmm, I made a file of roughtly 4,500,000 lines, and loadStrings() loaded them all.
When I increased the number of lines to 6,000,000, I got an OutOfMemoryError.
That's because loadStrings() fills an array, and if filled completely, it creates a new one, twice the size of the previous one, and copies all the lines to the new array.
If it is does that too quickly, leftover arrays remain in memory before being garbage collected, so we get this OOME.

" Using reader and writing each line to an arrayList(), [...] , is chronically slow"
How do you do that? It shouldn't be much slower than loadStrings(), actually.

A sketch like:

1. ArrayList<String> lines = new ArrayList<String>();
2.  
3. InputStream is = createInput("G:/Tmp/BigL.txt");
4. String line = null;
5. try
6. {
7.   BufferedReader reader = new BufferedReader(new java.io.InputStreamReader(is, "UTF-8"));
8.   while ((line = reader.readLine()) != null)
9.   {
10.     lines.add(line);
11.   }
12. }
13. catch (IOException e)
14. {
15.   e.printStackTrace();
16. }
17.  
18. println(lines.size());
19.  
20. exit();

is at least as fast as the loadStrings() version on my computer.
But I had to increase the memory setting of Processing to run it.